The sealing of pipe joints and other leak locations in pipes and pipelines is a critical concern, and proper sealing has become more important as efforts have increased to protect the environment. Liquid chemicals, sewage, toxic gases, and other fluid-like materials such as fine dust must be conducted through pipelines without leakage of the material from the pipeline and without contamination from outside. To seal pipe joints, pipeline installers typically encircle the joint with a cylindrical coupling consisting of either two semi-cylindrical pieces fastened together to clamp the pipe ends, or a single cylindrical piece having an axial slit which allows the coupling to be opened by an amount sufficient to fit over the pipe ends.
Annular gasket members, such as O-rings, may be placed around the pipe ends beneath the coupling to block the escape of fluid axially between the coupling and the pipe ends, but it is then necessary to block escape of fluid outwardly through the axial slit of the coupling. Several prior devices for this purpose have been developed, as described in U.S. Pat. Nos. 4,360,227; 1,607,943; 2,913,262; 3,153,550; 4,664,428, and 5,086,809.
U.S. Pat. No. 4,664,428, which is incorporated herein by reference in its entirety, describes a sealing plate spanning the axial slit of a coupling and contacting two O-rings positioned on opposite sides of the joint in the priprline. The sealing plate is positioned outside the O-rings, but between the O-rings and the coupling. The sealing plate has axial gaskets along its edges for preventing passage of fluid from between the O-rings to the outer surface of the sealing plate. This sealing plate has the disadvantage, however, that it can only be used with continuous annular O-rings which must be properly positioned on the pipe ends before positioning the sealing plate over the O-rings and then positioning the coupling over the sealing plate and O-rings. Placing O-rings around pipe ends may be difficult if there is insufficient room to maneuver the O-rings onto the pipe ends. Another disadvantage is that couplings having arcuate gasket members attached to the inside of the coupling cannot be used with such a sealing plate. In addition, during the positioning and tightening of the coupling, the O-rings may become misaligned or the sealing plate may become misaligned with respect to the O-rings.
U.S. Pat. No. 4,664,428 also describes a sealing gasket extending along an axial edge of the coupling so that the gasket is positioned between the axial edge and the inner surface of the coupling when the coupling is fixed around the pipe. Both approaches described in U.S. Pat. No. 4,664,428 have the disadvantage that in fitting the pipe coupling over the O-rings and other gaskets, the O-rings may buckle, deform, or be displaced, thereby allowing leakage. These problems in installation are particularly difficult when couplings are being placed underwater by divers, in confined areas, in open trenches or channels containing flowing water, or on existing pipelines to repair a joint or leak.
Thus, there is a need in the art for a pipe coupling that reliably seals all fluid paths from the interior of the pipe sections to the exterior of the pipe coupling. In addition, there is a need for a pipe coupling that can be installed reliably and conveniently in awkward situations. The inventions in my copending U.S. application Ser. No. 861,940 filed Apr. 2, 1992, entitled "Sealing Plate for a Pipe Coupling", have the disadvantage of a sealing plate which is a separate piece from the pipe coupling. The sealing plate must be placed first in proper position across the axial position of the leak location, and then the pipe coupling is closed around a pair of arcuate gaskets so that the arcuate gaskets engage the sealing pads of the sealing plate. Therefore, there is also a need in the art for a pipe coupling that is of one-piece construction and that provides ease of installation as well as sealing connections.